Page Types are a special Content Type in TYPO3. The basic structure is already defined in the TYPO3 Core. Content Blocks only adds new types to it. A minimal Page Type looks like this:
name: example/blog typeName: 942 fields: - identifier: additional_field type: Text
This will create a new Page Type entry above the page tree, which you can drag
and drop as usual. Your custom fields will be added after the
typeName has to be a numerical value for Page Types. There are
some reserved numbers, which you can’t use either: 1, 3, 4, 6, 7, 199, 254, 255.